1. Field of the Invention
The present invention relates to a communication apparatus for transmitting and/or receiving data such as an image, e.g., compressed encoded image and character code.
2. Description of the Prior Art
Of the image communication apparatus of this type, there is known a facsimile apparatus provided with an image memory.
In case that the same image data is to be sent to various destinations, or no connection is attained even if transmission to a certain destination is desired, use of the image memory is very advantageous since the image of an original can be stored in the image memory.
However, only the image signal of an original is stored in the image memory so that the user cannot judge if he is allowed to erase data in the image memory.
Conventionally, only an image having a certain size or image data suitable for a certain transmission mode has been allowed to be stored in the image memory. Therefore, sometimes it becomes impossible to transmit the image signal stored in the memory because of the reception mode of a partner machine. Thus, it becomes necessary to convert the amount of image data, such as a scan line density or the number of dots in one scan line.
In this case, particularly in case of reducing the amount of data, character information regarding a sender and transmission time to be recorded in a relatively small space is also reduced in size, thus making it not legible at the partner device.
Furthermore, image data once stored in the image memory cannot be erased unless the operator works to such effect, thereby resulting in ineffective usage of the image memory and complicated operation.
Some apparatus have been proposed wherein image data is automatically erased after a lapse of a certain time. With such apparatus, however, unnecessary erasure of image data may happen in case of a time designated transmission mode. Thus, it is very inconvenient.
Conventionally, a buffer memory for temporarily storing encoded image data during transmission has been provided together with the image memory. However, in case that the buffer memory of a large capacity is used as the image memory, there is no space for temporarily storing encoded image data during an original transmission if image data is already stored in the buffer memory.
While storing image data in the image memory, EOL code indicative of the end of one line of image data is also stored. EOL code together with image data is transmitted to detect the end of one line at the receiving side.
EOL code to be used in transmission conforms with Recommendation of CCITT. However, some EOL code has the same bit length as that of MH code indicating the line length. Thus, it is difficult to search EOL code in a short time.
As above, use of the image memory has been associated with various problems.